A three-dimensional stacked memory stacked in a vertical direction and processed at a time has been suggested as a NAND flash memory.
In the three-dimensional stacked memory, a cylindrical hole (memory hole) is formed at a time in multiple electrodes stacked on a semiconductor substrate, and a memory film is formed on the inner wall of the hole, and thereafter polysilicon (silicon pillar) is formed in the hole. As a result, a NAND string including multiple MONOS memory cells connected in series in the stacking direction, with the silicon pillar being the channel, can be formed at a time.
In the three-dimensional stacked memory, the U-shaped silicon pillar is used as the channel of the memory string. The U-shaped silicon pillar includes a pair of pillar-shaped portions and a connection portion connecting them at the lower ends. At the upper portion, one of the pair of pillar-shaped portions is connected to a bit line, and the other of them is connected to a source line.